Since I tripped across this pic, and I didn't know much myself about the different generations except that Gen 3 was the first generation for the Tactical Rail until I researched it myself.... Figured it would be a good thread idea for the gurus to educate the newer Glock owners and those who are curious.

Basic reason for adding the tacitcal rail was for law enforcement. plus a much needed better grip. GEN. 3's raised the bar for sure.

Adding the finger grooves and thumb was huge for the 3. For sure, some worthwhile changes for Gen 3. I've yet to use my tactical rail. I instantly put Trigicon Night Sights on my G23 Gen 3 after I bought it. Didn't feel the need for the light so the bad guy could see me. And laser was expensive. Still a cool option to have though in the event I need it, I have it.

Positive about that? NONE of the Sub Compact got the Tactical Rail as far I know of, since there is not enough room on the frame, so it is very well a Gen 3. Never heard of a Gen 2.5.

Well, it may not be officially a 2.5 but it is commonly referred to it that way. Did find this though.

"- 1st Generation has the smooth, rounded “pebble-grip”.
- 2nd Generation has the “Grenade-style” checkering with NO fingergrooves (see picture).
- 3rd Generation has BOTH fingergrooves AND accessory rail on the front dustcover.
- If you have a subcompact (G-26, -27, -28, -29, -30, -33, -36) OR a “transition model” when Glock was putting fingergrooves but no accessory rail, then you have a 2.5 Generation. There is even a slight variation here, as some of the earliest G-26 & G-27s had smooth fingergrooves, without checkering in-between the grooves. Some people do not count the sub-compacts as 2.5 Gen since they came out after the 3rd Gen frames were already being made. Note: newer -29, -30 are now coming with rails."

That makes it much more clear. So there is a 2 to 3 transition frame. I too would be one of those that would not count a sub compact as a 2.5 or even transition frame, if it had all the other features of the Gen 3 less the rail, like chambered round indicator that Gen 3 also has that the Gen 1 and 2 don't have.

Had I followed the link associated with that pic, I'd have found this info much sooner. This is good stuff. I even learned a couple things here. So here it is for the rest of us.

First GenerationThese are the granddaddy of the whole Austrian designed family in 1982. It was this, now "old school" design that Gaston Glock carried down from the mountains and gave to the people. Several late models, such as the Glock 26, 29, 34 and 35, were never made in this style.

Gen 1 pistols are easily identified by their blocky, clunky, grips without any finger grooves or ridges.

Second GenerationWhen the year 1988 dawned, the next generation of combat polymer was dubbed worthy and Gen 2 of the Glock was brought forth into the world. This improvement was mainly all about the grip: it improved it. With checkering on the front and serrations on the back, Glock owners didn't have to feel silly buying skateboard tape anymore. Internally, the recoil spring was changed to an encapsulated type, the trigger pull was increased slightly, and a better drop-free magazine was introduced.

In addition, to ensure better ATF compliance, the serial number plate was embedded to the frame of the gun. Today, when old Glock frames go to that great beyond and are literally melted down to be recycled, the factory just cuts those serial numbered ends off and presents them for verification.

Third GenerationBy 1997, Gen 2 Glocks were pass and Gen 1s were virtual dinosaurs due to the introduction of the third installment in the G series evolution. In this development an under-barrel accessory rail, loaded chamber indicator (hello CA compliance!), heavier breech locking block, and most importantly, finger grooves and thumb rests were added to the grip.

Fourth GenerationThese pistols, introduced in 2010 are one of the latest evolutions in the Glock stages of development. Taking the Gen 3 guns (which are still in production) and building on them, the Gen 4 adds a larger and reversible magazine release, three different-sized back straps for the back of the grip, and a rough textured finish (RTF3) for a more positive gripping surface. (Note- Some Gen 3 guns were made with a RTF and are occasionally referred to as 3.5s.)
The last difference is internal and can't be seen at first glance without disassembly-- dual recoil springs, instead of the encapsulated single recoil springs of Gen 2 and 3 models. Unlike past models, these new guns have ""Gen4" roll marked on the slide to take out the guesswork.

No matter what generation your past, present, or future Glock is, all have a well-deserved reputation for rugged durability, accuracy, and reliability. And you can be sure that the Gen 5 guns are on the way.